A few years ago I waded through glassy shallows off Mactan Island, a Philippine map-speck little more than an hour’s flight southeast of Manila. The sun was searing that afternoon, although the knee-deep water was kind enough to the skin. Slow-motion steps eased me across a gaudy bottom, sneakers carefully avoiding coral heads, sea urchins, anemones, sponge growths, starfish. Trailing like mermaid tresses, algal strands wound around and between my bare legs.
Four centuries earlier, Ferdinand Magellan had sloshed shoreward through these same biotic shallows, suddenly to be ambushed and slain by hostile natives. Today, only a stone’s throw inland, a decaying monument stands to remind the very occasional visitor of the fallen circumnavigator’s achievement.
Accompanying me was Evaristo Zambo, from nearby Cebu, who makes a living collecting fancy seashells for export to the souvenir markets of America and Europe. His business prospers, for the Indo-Pacific area in general and the Philippine archipelago in particular comprise the world’s most bountiful mollusc habitats, with denizens ranging from tiny cockles and exquisitely patterned cowries, to giant clams of a quarter-ton.
Before setting out that morning, Evaristo, a bit self-consciously, had pulled from his pocket a prickly walnut-sized seashell. Homalocantha zamboi, he called it—a species of heretofore unknown mollusc latinized by American conchologists to whom he had sent duplicates for identification. What a foolish name is Zambo to be immortalized by science, he remarked with a grin. But his pride was apparent and quite forgivable, for with some 90,000 mollusc species known worldwide (and perhaps an equal number now extinct), not too many additional ones remain to be discovered and classified.
Evaristo wasn’t resting on his laurels. I stood by as he waded about, gently upending coral clumps, here one, there one, to examine their hidden undersides. Abruptly, and without a sound, he beckoned me, pointing down at the sundappled reef floor to a curious lump no larger than the first joint of my index finger.
Sinking splashlessly to my knees on an adjacent patch of smooth sandy bottom, my eyes zoomed in on the target. Resting there amid coral debris was a living female cowrie (of the Gastropoda or snail class of molluscs) astride her clutch of pinhead-size egg capsules. Zambo was about to snatch up the lot for his collecting bag, when I gently restrained him. A brooding cowrie was something I couldn’t bear to see disturbed.
Cowries are in fact one of the few marine molluscs to tend their eggs in hen-like fashion—not to warm or incubate but to guard them against hungry predators lurking in every underwater shadow. Two martian antennae standing alert from the matron’s head began scanning back and forth, obviously aware now of foreign presences above.
Within three weeks, the eggs would yield minute larvae for a life of hazardous independence, survivors settling on coral branchings or reef bottom. A delicate shield would develop over each growing babe, gradually to thicken, harden, and then to mould in and under itself to create a wondrous life-time dwelling for one of a new generation of cowrie—housing gills, viscera, foot, mantle, gonads, and all.
This brooder’s shell was faun-brown, its upper surface neatly dappled with white to justify the Latin name miliaris,spotted, blotched. Hard and porcelainous as chinaware, the shell was continuously being enlarged, strengthened, colored, and designed by secretions from the encompassing mantle membrane. At any slight alarm, the mantle would pull back into the shell’s interior, then at the all-clear, venture out again—a lacy film warily sliding up over the shell’s outer surface. Some gastropods have attached to the foot tissue a horny plate or disc which in an emergency swiftly retracts as a protective cover for the creature’s internal soft parts; in others (for example, the Caribbean Pink Conch) the structure is scimitar-shaped, providing means for a crude sort of one-legged, hopping locomotion.
During the 18th and 19th centuries, seashells figured prominently in both public and private collections—voguish objets d’art to be displayed in the gentleman’s curio cabinet or on his mantelpiece, Their charm seems to have been derived from graceful shape, smooth patina, diversity of color and pattern, and in some instances extreme rarity. As for cowries, their family name Cypraeidae stems from the Mediterranean island of Cyprus, a place classically associated with the goddess Aphrodite. Early shell classifiers drew a resemblance between the cowrie’s aperture and the aphroditic genital orifice.
Not that shell collecting was ever quite the equivalent of, say, the accumulation of postage stamps, . . . . As far back as two millennia B. C. the Chinese used shells for money. When metal came into coinage, their contours lingered on the stampings. Carried into central and east Africa from reefs and islands of the Indian Ocean, seashells, especially cowries, continued to be a medium of exchange: 2500 for a cow, 25 for a chicken. In fact, one species bears the name Cypraea moneta.Shells were widely treasured for sewn-on designs and headdress ornamentation. Tiger and Map cowries were thought to whisper intelligibly when held close to the ear— advice usually relating to matters of romance and fertility. South Sea islanders dangled cowries and other choice sea-shells on fishing nets to insure bounteous catches; and the especially rare and handsome Golden Cowrie, Cypraea aurantium, was worn by Melanesian royalty. In certain parts of southeast Asia a deceased ruler’s mouth was stuffed with nine first-quality cowries, while feudal lords rated only seven, high officials five, clerks three, common people one. And how about the sometime use of cowries as artificial eyes for Egyptian mummies!
Following the 1492 New World tidings, European sails were resolutely set for exotic places, where beaches and reefs were often rich in seashells. Elizabeth Bligh’s collection grew with each return of her illustrious husband, and many of her shells now reside in the British Museum. Captain Cook’s officers and men crammed their sea chests with molluscan bounty. Connoisseurs in Amsterdam and Antwerp were enchanted by previously unknown species brought from the Dutch East Indies by returning officials and colonialists.
Brisk trading in the cultural centers of Europe during the 1700—1800’s reflected a full-blown preoccupation with Gifts from the Sea. Even crowned heads were lured by the fantasia of univalves and bivalves. Queen Ulrica of Sweden (1720—1782) kept her thousands of seashells in a special museum; it was she who supplied Linnaeus with specimens needed during the development of his bold new system of binomial no-menclature. The Duchess of Portland (1714—1785) accumulated the most celebrated and costly shell assemblage in England; after her death, it had to be broken up and sold to meet the debts she had thus incurred. Peter the Great of Russia (1672—1725) was a shell enthusiast, and Empress Catherine II was the proud owner of a magnificent Precious Wentletrap. The husband of Maria Theresa, Kaiser Franz I, is reported to have purchased a Precious Wentletrap for 4000 guilders. Wentletraps today go for about five dollars each, the price gap obviously reflecting their rarity in 1750, their abundance in the late 1900’s. All such princely shell fanciers employed brokers and traders ever on the alert for new finds; yet no one in those days had any inkling of the hundreds, perhaps thousands, of bizarre new species later to be discovered in the sea’s great depths, where all is dark, pressurized, and cold.
Malacologist R. Tucker Abbott notes that since the invention of the printing press, more than 4000 books and some 91,000 articles and monographs have been devoted exclusively to molluscs and their diversiformic shells. Early volumes bear such intriguing titles as Recreation for the Eyes and the Mind (1681); Historiae Conchyliorum (1685); Delights of the Eyes and the Soul (1760).
Predating the lot were such seashell expositors as Aristotle and Pliny the Elder; and Suetonius relates how the mad Roman Emperor Caligula in the year 40 A. D. lined up his legions on the shores of Gaul, primed to invade isles across the Channel. Suddenly the demented despot had a quirky change of mood, ordering the troops instead to march up and down the beaches in search of seashells. Carrying “the spoils of conquered ocean,” Caligula returned home in self-acclaimed triumph.
So enthralling have men found the subject of seashells, that even Edgar Alien Poe was persuaded in 1839 to author a conchology guidebook which, alas, proved at least in part to be plagiarism of a work printed six years earlier in Glasgow by a Captain Thomas Brown.
Of the some 40,000 snail (gastropod) molluscs, those of the family Conidae earn high marks both for beauty and treachery. I became acquainted with a notorious member of the clan while strolling one day on a reef in Kaneohe Bay, northeast of Honolulu. There I met a young zoologist named Alan J. Kohn, then at the University of Hawaii. “Are you one of the Cones?” I asked, sinking to the very lowest form of pun play.
He extended a gloved hand to display a conical shell exquisitely adorned with brownish tent-shaped markings. “Yes,” he replied, “spelled with a K,” adding, “but this one, spelled with a C, is about as mean as they come,”
As it turned out, Kohn was researching the cone family’s several dangerous members. In later laboratory experiments he was able to show that the sting of Conus textile and also that of Conus geographus (the two most venomous) were designed by Nature not to inflict hurt on the careless shell collector but rather to secure such comestibles as small fishes, worms, and the like, tenanting the reef habitat. The kill is by means of a minute hollow harpoon held in the animal’s mouth (hence the suborder Toxoglossa, or poison-tongued). Always cocked and ready to fire, the weapon is connected by means of a thread-like tube to a gland elaborating a poison chemically related to curare. Any marine Lilliputian venturing close triggers the mechanism, instantly to be impaled and injected. Death quickly follows, and the executioner feeds well. Usually ripped away either during the firing or by the victim’s agonizing thrashings, the spent hypodermic is replaced from a stock of others ready within a quiver-like pouch near the cone’s head.
If a textile or geographus is picked up by the bare hand, the harpoon barb directs itself toward any point of contact with finger or palm. Of the 37 documented cases of man-stung-by-cone, ten were summarily fatal, the others excruciatingly painful. On a subsequent visit to the Great Barrier Reef of Australia, I was forever being cautioned to handle no live cone unless properly gloved or certain beyond doubt of its being neither of the two dread species.
On the brighter side, most Conidae are quite innocuous. Take, for instance, Conus gloriamaris, the Glory-of-the-Sea, once the most coveted and valued of seashells. Up to 1837 only six were known, and they were featured at every major shell show or auction, each appraised for far more than its weight in gold, Then a British collector, probing a Philippine reef (not far, in fact, from where Zambo and I had done our combing), came upon two Glories-of-the-Sea clinging, just like our cowrie, to the underside of a coral head.
Resulting front-page shell news, along with that of subsequent finds by SCUBA collectors on other tropical reefs, had the eventual effect of devaluating the Glory-of-the-Sea, although even today specimens are not exactly given away, About 300 currently repose in private and scientific collections. In 1951 a thief, breaking through a glass case in New York’s American Museum of Natural History, seized a gloriamaris and disappeared into the crowd, apparently unaware that his loot, worth in the mid-1800’s a king’s ransom, was by the mid-1900’s no great treasure. The deluded thief was never apprehended nor the shell recovered. Better had he sought a cowrie named Cypraea leucodon, of which only three specimens are known, each with a current market value of $3,000 upwards.
Replacing gloriamaris as queen of cones is one bearing the equally rapturous name Glory-of-India, of which fewer than two dozen are known. Their presently fat pricetag will no doubt be sustained until some lucky collector dredging in the Indian Ocean uncovers a new lode. Pending that day, the Glory-of-India may perhaps provide the central theme for a novel, as did Glory-of-the-Sea in Victorian days. And speaking of rapture, page through any modern seashell book and note the poetic range of common names: Bleeding Tooth, Flame, Pyramid, Sundial, Measled, Mitre, Venus Comb, Eye of Judas, Ziczac, Distaff, Pontifical, Prometheus, Lion’s Paw. . . .
Another especially notable family of univalve seashells are the Muricidae, whose history runs back almost as far as man’s own recorded origin. By the 15th century B. C., Phoenicians of the powerful city-state of Tyre had learned to extract a lavishly colorful dye from the body tissues of Muricidae specimens. Legend relates how in pre-Tyrian times a shepherd’s dog came one day upon a seashell stranded on the beach. Sniffing it as potentially tasty, the sheep dog crunched on the spiny object until a yellowish mucus exuded which upon coming in contact with the air and sunlight was oxydized to a garish hue of red-blue. The dog returned to its master, tongue fuchsia-dyed. Tyrian Royal Purple had been discovered.
Because of the strenuous dive-and-search effort required to find adequate numbers of Murex specimens, each yielding only a droplet of the precious mucus, the dye was very dear. Before long, monarchs and would-be conquerors were vying for its control and exploitation. Strategically located and superbly fortified, Tyre sent out its triremes to probe distant coasts and reefs for virgin Murex beds, even as far north as the British Isles. Tyre (which, incidentally, also provided history with the Jezebel of Old Testament disrepute; and earlier Phoenicians, our first alphabet) seems thus to have grown and prospered, at least in part, from a seashell no larger than a man’s fist. So great was her power, so durable her men and walls, that it took even the mighty Alexander many months of siege and a series of unprecedented military stratagems to overcome the island fortress in 332 B. C. and thus to control its largely mollusc-derived fortunes.
Because of its rarity and consequent value, cloth dyed with Tyrian Purple was initially limited in use to temple hangings, later for garments worn ceremonially by priests. Eventually kings and emperors adopted the color, and royal progeny were said to have been “born to the purple.” With the advent of the Christian era, cloth of Tyrian Purple draped holy altars and also, as in pagan times, robed the high clergy. The ship carrying Antony and Cleopatra in the battle of Actium is described as having purple sails, the ultimate symbol of pomp and power.
When Alexander’s troops finally overran the Susa store-houses of accumulated Persian treasure, loot taken included vast amounts of Murex-dyed fabric said to have been worth the equivalent of $12,000 a pound. Plutarch writes of it: “. . . purple, that had been laid up there an hundred and ninety years, and yet kept its colour as fresh and lively as at first.” Reddish-purple homespun worn by certain indigenes of Central and South America has led some ethnologists to speculate on whether Phoenician mariners may have touched there in very ancient times.
Shell lore runs back even further, in fact some 600 million years, for molluscs evolved earlier than most other animal forms. Their hard parts, derived from the sea’s dissolved minerals, left so complete and durable a record, that paleontologists have had a heyday analyzing molluscan evolution, its spurts, slowdowns, innovations, extinctions, habitat changes. Shell fossils found far inland were in medieval times regarded as the devil’s work, placed there to tempt man away from the biblical version of creation. And it is well known that during the famous 19th century voyage of H. M. S. Beagle, a young Charles Darwin was profoundly influenced by fossil seashells he stumbled upon while hiking among Andean peaks twelve thousand feet above the coast. Had God (or the devil) sequestered seashells in so exalted a location or had the ocean floor simply soared and shifted laterally during the course of geological eons? Darwin’s private answer had the effect of diverting him from a career in the Anglican priest-hood so fervently hoped for by his family. From Darwin’s uniquely creative mind came instead the heretic Origin of Species, which since the late 1800’s has rocked the foundations of Christian thought:
Cultural anthropologists often encounter molluscs, especially bivalves of the Pectinidae family, otherwise known as pectens or scallops. Picture early man living near the sea, devouring molluscs’ meaty parts, then using the shells as scrapers, blades, spearheads, utensils. Huge triton shells pierced near the tapered end made sonorous trumpets, and mother-of-pearl provided fishing hooks as well as exquisite ornamentation.
The idea of Aphrodite (Venus) arising fully formed from a scallop shell repeated itself endlessly in classical times, as did a belief that the Creator Himself emerged from a conch. In neither case is the symbolism clear, although among coastal peoples, an intimate and crucial relationship quite obviously existed between man and the sea. The scallop first appeared as an art motif on mosaic floors, then on walls, pillars, pavements, finally to emerge as something of religious, mystic, or sexual connotation. Why, incidentally, should the materialization of Aphrodite from a scallop seem any more extraordinary than that of Eve from a rib?
The Apostle James (Santiago) was posthumously associated with the scallop. The linkage appears to have been made when in medieval times his purported remains were discovered in Spain, near Compostela. Some miles from the burial site were shell heaps left there by erstwhile scallop eaters. No one knows whose idea it was, but those otherwise worthless shell halves were sold to pilgrims as badges certifying a visit to the sacred grave. Crusaders often bore a design of the mystic Santiago scallop on their shields or vestments. And to this day the scallop appears on the coat-of-arms of many a celebrated family, not to more than mention its reknown as the trademark of an international petroleum company.
Members of a distantly related bivalve group are the so-called Window Pane shells, first used by the Filipinos for making translucent panels. I visited a Manila suburb whose cottage industry involved the preparation and cutting of this unique species. Rows of bushel baskets were piled high with papery shells whose organic insides had been discarded. Not that there was much to discard, for these abundant tropical bivalves are so thin and their halves so tightly fitted, that one wonders how any organism can live in between. Hold a freshly dredged live Window Pane oyster to the sun and see the outlines of muscles and vital organs, as though fluoroscoped. To this day, Filipinos use them for both indoor and outdoor panelling; and in decorative lampshades and place mats they appeal to Western taste (the light falling on my typewriter at this moment comes through a Placuna placenta lampshade I bought not in the Orient but on Madison Avenue).
Heavily weighting the other end of the bivalve spectrum is the family Tridacnidae of Indo-Pacific waters. Except for the giant squid of northern seas, Tridacna gigas is the most massive and formidable of molluscs, its length attaining 4 1/2 feet, its width half that, with a pair of cleaned valves tipping the scales maximally at 580 pounds. The clam rests on the reef floor, its hinge embedded in sand or wedged in the coral platform, with maw always oriented skyward so as to receive optimal sunlight for the photosynthetic benefit of symbiotic algal cells residing by the millions within the clam’s fleshy mantle tissues.
A pair of such powerful clam valves closing on the legs of a careless pearl diver or SCUBA swimmer is a familiar Sunday Supplement ploy. But there is no authenticated instance of a “man-eating” tridacnid living up to so fearsome a reputation. The gruesome possibility nevertheless crept into my mind one day off Green Island, Queensland, as I approached not a giant of the species but one about the size of a large pumpkin. I lowered the end of my walking stick between the gaping valves. They came together quite slowly but finally so tightly that by lifting upwards on the free end of the stick, I was able to draw the 40-pound behemoth nearly out of its tide pool home, Accounting for the clam’s viselike tenacity was a thick adductor muscle attached at each end to the valves’ inner opposite surfaces.
Stranded seamen have survived on Tridacna meat, reporting it to be tasty, though tough and sinewy. In one of his South Sea logs, Captain Cook writes of “. . . cockles of so enormous size that one of them was more that two men could eat.” Pearls as big as golf balls sometimes found in these giant clams are relatively worthless.
I recall visiting a marine collector in Zamboanga. His entire front yard was stacked high with Tridacna gigas half-shells, all white and gleaming in the tropic sun. When I asked why the glut, the collector commented a bit archly that the good people of Connecticut, Virginia, and other distant states were beginning to acquire a taste for outdoor bird baths. I could have added that at least one of the world’s great cathedrals uses a Tridacna shell as a baptismal font. I asked how much he wanted for one. Well, there on the spot, five dollars; crated and delivered to my home in the States, no less than six hundred.
The family Volutidae (scroll shells) comprises about 200 species, most of which live on or in tropical reef bottoms of moderate depth. With their short spires and flaring apertures, volutes are among the most attractive of marine snails, with surface markings carried out in subtle tones of ivory, orange, and brown.
One species, often called the Heron Island volute, is found only in the vicinity of a wee, sun-drenched, wide-beached isle of that name, off Australia’s northeast coast. Tides there rise and fall as much as 20 feet, twice monthly exposing vast prairies of living coral—teeming habitat of a billion molluscs. When we arrived on Heron, collecting fever among the vacationists was running high, and my wife and I were almost immediately drawn into the buzz about seashells. Shelling was fabulous here, we were assured. In front of nearly each beach cottage, drying in the sun, were ranks of seashells freshly off the surrounding reef, including, of course, some species of volutes. But, moaned the shell buffs, not a single Cymbiola pulchra, pride of Heron Island, nor had any been reported during the entire year. With more than a hint of exaggeration, we were told that a fine pulchra (as if inlaid with diamonds and gold) could easily command a three or four figure price.
Next day shortly before the turn of the tide, my wife and I waded out onto the reef, where lucite-clear pools, lined with forests of staghorns, organ pipe, and other corals, sheltered blue and orange damsel fishes which seemed to be enjoying a quiet low-tide hour free of pounding surf. Displayed like jewels in a Tiffany case were also seastars, bryozoans, bivalves, univalves, along with shimmerings of other marine invertebrates.
While I set my camera, my wife wandered off for some sandy shallows where the sea at the moment was not more than shin-deep. Each time I glanced up, I saw her stooping, once here, once there, again and again. When at last she beckoned to me urgently, I splashed to her side.”I’ve found pulchra,” she yelled excitedly: “Look!” There in her collecting basket I counted not one but 18 of the rare Volutidae.
This extraordinary haul caused a sensation when we returned to the guest compound. Next day at low tide almost every person on the island (no fewer than 40), many equipped with rakes or trowels and all intensely competitive, were swarming on those same sand shallows. But not a single other pulchra was found, either that day or during the remainder of our six-week stay.
The fact that my wife had stumbled onto a virtual Cornstock lode was in itself no great miracle. Clearly, some chance interaction of tidal, meteorological, nutritional, and perhaps reproductive factors had momentarily lured a pulchra population up from its safer sub-sand abode. Of greater interest remains the fact that a single molluscan species exists endemically only in this one Pacific niche. Such explanatory terms as geographic or reproductive isolation do not in this instance fit, for the sea here and for hundreds of miles around is quite uniform, and the movement of larvae-dispersing currents general, We left Heron Island with a bag of sumptuous sea-shells, and with more questions than answers.
The molluscan firmament sparkles not only with volutes, cowries, cones, murexes, and scallops but also with scores of other varieties with such colorfully descriptive names as: heart cockles, hammer and thorny oysters, turkey wings, ark shells, mitres, slit shells. . . . There are in fact under the Phylum Mollusca nearly 500 distinct families and subfamilies, several of whose members have no shells. Nudibranchs (exposed-gill molluscs), for example, have little or no calcereous component, a lack shared by some squids and octopi (also bona fide molluscs), the latter two gracing the planet’s seas with huge piercing eyes, swiftly changing hues, an advanced system for jet propulsion and, in the case of some deep-sea species, organs of dazzling bioluminescence.
Among these shell-less forms, nudibranchs are certainly the most arrestingly chromatic, many resembling paint daubs on the palette of an artist given to haphazard mixing. In almost any habitat occupied by shelled molluscs, nudibranchs will be there too, graceful and gaudy. Living in California as a boy, I searched for them on the shores of Monterey and also, farther north, off Point Arena. At that age I had had no science training, simply the natural curiosities of childhood. This was long before SCUBA and snorkling gear had become everyday accessories for the shore visitor; one simply looked hard and occasionally dunked his head and opened his eyes for a moment of underwater orientation.
In tide pools and amid shallow kelp beds there, I sought the shell-less molluscs, like a child seeking flowers in the thick grass of an early spring meadow. They were known to me only as sea slugs. I recall the precise moment I sighted something of bright blue and yellow undulating slowly over the surface of a seaweed frond. Easing myself waist deep into the chilling water, I got as near as possible. At one of its ends the finger-long slug wore two stalking antennae, and at the other, a tuft of elegant reddish plumes which comprised the naked gills implied by the name nudibranch.There was no shell, although I learned much later than some species during early stages of embryonic development have vestiges of calcareous material, attesting to the bearer’s evolutionary pedigree.
For a time the beautiful slug seemed to promenade just for me; then slowly it slipped to the underside of the frond, probably in search of a favorite meal of hydroids and sea anemones. These latter are in themselves bizarre, each possessing embedded in its surface tissues thousands of highly specialized cells capable of injecting any aggressor with a thoroughly noxious toxin. But nature has equipped the slug with means for countering this hazard: before biting off a piece of delicious coelenterate, it exudes over the site a mass of thick mucus which prevents any sting cells there from firing. During digestion the temporarily immobilized sting cells are somehow eased through the nudibranch’s intestinal and body tissues, finally to be planted in its own back where, now again facing the open, they resume an erect and cocked position, ready, with their Catling equipment, to wither any threatener of their host. By so making use of stolen weapons, the nudibranch has obtained a powerful armamentarium of its own.
But not all nudibranchs are so devious. Some feed only on harmless fish eggs which, being pure protein, are totally metabolized to leave no waste; indeed, such sea slugs have no anal aperture, for they need none. What an improvement over the waste-disposal vagaries of higher animals!
Lemon yellow, electric blue, fire-engine red, flaming orange—virtually every wavelength of the color spectrum provides the slug with enhanced technicolor. For what purpose: Camouflage? Warning? Courtship strutting? Species recognition? Nobody really knows. To my youthful mind, the creatures were simply beautiful fragments of rainbow which Nature had thoughtfully dropped into the sea.
I recall another day of youthful exploration when I clambered over slippery rocks of the thundering, often fog-bound coast of Mendocino County. At the edge of a mirrored pool I hesitated, spotting within arm’s reach in the water an abalone stuck fast to the plunging rock wall. I lay flat on my belly and, holding a heavy tire iron as a wedging instrument, lurched down for the Haliotis there. Probing this way and that, I finally maneuvered the iron’s tip under the shell’s edge, then pried hard. Now the creature was beginning to loosen, and at last it snapped free. But before I could seize it, the promised meal went zigzaging down to disappear in the pool’s dark depths.
As to the abalone’s saucerlike form and its marvelously iridescent inner curves, few would regard these as comprising a spiral. Yet close perusal of one end reveals a tiny whorl whose last grand flair becomes the entire shell. Geometric ratios and growth characteristics are, of course, quite different from those of other coiled molluscs, yet a spiral the abalone shell truly is.
Spirally conceived too, is a mollusc of very ancient evolutionary origin, known as the Chambered Nautilus. Some 400 million years ago its ancestry comprised more than 10,000 distinct species, almost all having long since become extinct, but not before leaving a fascinating paleontological record. One species possessed a shell an unbelievable 15 feet across; another’s whorl was eight feet from edge to edge. How and why these gargantuas became extinct is obscure, for most of them evolved and lived in a relatively unchanging deep-sea habitat.
Oliver Wendell Holmes could not have known much about these ancient ones when a century ago he hailed the living Chambered Nautilus (Nautilus pompilius Linné) as a “ship of pearl, which . . .sails the unshadowed main. . . .” Holmes’s biology was quite correct, for Nautilus to this day dwells only in the sea’s shadowless deeps. Less poetic men have regarded this coiled marvel as a logarithmic spiral—one of universal appeal and mystery to both philosopher and mathematician. From Pythagoras onward, the fact that Nautilus and similarly coiled shells can retain their logarithmic fidelity, even while in a state of circularly expanding growth, has boggled the best minds. What remarkable internal clockwork must such a mollusc possess, what incredible biologic slide rules and internal computers to compose so intricate and constantly changing a set of geometric directives!
Nautilus builds its ever-enlarging chambers set apart by successive walls, while residing only in the chamber most lately formed. This led Holmes in his famous poem to tell how Nautilus “Year after year . . . spread his lustrous coil; Still, as the spiral grew, Stretched in his last-found home, and knew the old no more.” In the finale, Holmes makes the thundering entreaty: “Build thee more stately mansions, O my soul. . . . Leave thy low-vaulted past; Till thou at length art free.”
But, alas, not all figurative imagery based on the Nautilus- type mollusc is apt, for as prescribed by the laws of physics and the demands of nutrition, growth on an unlimited logarithmic scale would inevitably lead to a breakdown in the logistics of provisioning, and inexorably to biological death.
Perhaps it was a perception of this that led Holmes so desperately to cry for more stately mansions. Do his words imply an intimation of continuing mental or spiritual development, perhaps leading to some sort of transcendent “reality” unhampered by nutritionally or logarithmically imposed limitations?
Anticipating Holmes by nearly a century, conchologist Emanuel Mendes da Costa in 1778 described a cabinet of seashells as a “volume of fine wrote sermons.”
My own unremarkable conclusion is that the molluscan form possesses a curious élan which, since the earliest days of human history, has either overtly or subliminally been recognized by countless persons—beachcomber, reef explorer, artist, craftsman, mythologist, philosopher, scientist, connoisseur.